This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A309147 #11 Jul 27 2019 11:19:58
%S A309147 1,4,28,356
%N A309147 Least k such that the rank of the elliptic curve y^2 = x^3 + (k^2 + 6*k - 3)*x^2 - 16*k*x is n.
%H A309147 Allan J. MacLeod, <a href="http://web.archive.org/web/20100125135648/http://maths.paisley.ac.uk/allanm/ECRNT/knight/knintro.htm">Knight's Problem</a>
%o A309147 (PARI) {a(n) = my(k=1); while(ellanalyticrank(ellinit([0, k^2+6*k-3, 0, -16*k, 0]))[1]<>n, k++); k}
%Y A309147 Cf. A309144, A309146.
%K A309147 nonn,more,hard
%O A309147 0,2
%A A309147 _Seiichi Manyama_, Jul 14 2019